Patent GB-179033-A (GB)
Title: Improvements in railway signalling
IPC: B61L23/12
Filed: 1921-03-18
Abstract: 179,033. Sykes Interlocking Signal Co., Ltd., W. R., Sykes, F. J., and Lascelles, T. S. March 18, 1921. Signalling instruments; interlocking signalling instruments; combined electrical and mechanical systems, non-automatic.-In a three-wire electric lock-and-block system of signalling on double lines, of which Fig. 1 shows only the " acceptance " portion of the instrument at the exit end B and the sending portion of the instrument at the entrance end A of a section, with the line wire for controlling traffic from A to B, means are provided at the entrance end whereby the electrically controlled lock 47, which normally prevents the use of the hand lever or other means for clearing the signal S, is released as a result of the closure of its circuit at a normally open switch 20, by the energization of the main winding 17 of a compound-wound sticking-relay R<a> when this winding is energized by a current, which exceeds a predetermined magnitude, namely, that transmitted over the line wire 16 from the battery 40 by the operation of the plunger P. Current of a low strength from the battery 41 at B or current from the battery 22 at A through a high resistance winding 18, causes the relay R<a> to retain its armature. A switch operated by the hand lever is arranged so that when the signal lever is pulled off, the sticking circuit to the relay is opened at contact 44 and the relay is cut off from the line wire at contact 45, and the line wire is earthed at contact 46. At the exit end B of the section, a relay R<b> is provided, the circuit to which is normally broken at a contact adapted for actuation by a train passing a point at or beyond the end of the section, such as the treadle T. The armature of the relay R<b> is normally held in its attracted position by a detent 25 which is mechanically removed as the plunger P is pressed inwardly to give " line clear." The plunger P is capable of movement in two mutually-transverse directions, both of which are controlled by locks operated by electromagnets 27, 30, the release of which is dependent upon the armature 23 of the relay Rb being in its raised position. The releasing circuit also includes a contact 49 on the hand lever for the signal M which must be normal, and a press button 28. To give " line clear " to A, the switch 28 is closed and the lock 26 withdrawn by energization of the ma.gnet 27 by current from battery 39 over contacts 23, 49, 28. The plunger P is then pushed inwardly and releases the detent 25 from the armature of relay Rb so that the contact 23 is opened (thus preventing a second release of plunger P) and contact 24 is closed and a circuit is made from battery 40 over contacts 34, 24, 37, indicator 14<b>, line wire 16, indicator 14a, contact 45, and winding 17 of relay R<a>. On the, return to normal of the plunger P the weaker battery 41 is substituted for the battery 40 by the closing of contact 33, the current being sufficient to retain the armature of relay R<a>, contact 19 of which closes a circuit from a battery 22 over contacts 44, 19 to the winding 18 and contact 20 closes the circuit to the lever-lock magnet 47 enabling the clearance of the signal S. Relay R<a> is cut out at contact 45 and its armatures drop, and the line wire is earthed over contact 46. When the train has entered the section, the bell signal from A to B is acknowledged by the rotation of the plunger P to close contact 38 and substitute the reversed battery 42 for the battery 41, thereby giving " Train on line " in both indicators. The plunger is looked in its rotated position by the pawl 29. The train passing clear of the section closes at treadle T a circuit from battery T<2> over contact 50 on the lever for signal M to the relay Rb which resets its armatures and enables the withdrawal of the lock 29 for replacement of the plunger P thereby opening the line circuit and causing both indicators to show " line closed." At junctions the receiving instruments relating to convergent tracks are interlocked by causing the circuit of the plunger-lock of each instrument to pass through an additional contact on the relay Rb at each other instrument so that if any one relay armature has been released no other plunger can be unlocked until the first train has passed or the acceptance has been cancelled. Any acceptance may be cancelled by the use of the keys C<a>, C<b>, which must be simultaneously operated after exchange of signals by the operators. These close a circuit from battery 21, over contacts 20, 43 (if the signal lever is at " normal ") key C<a>, line wire 16, key C<b> to relay Rb, which is thus reset.